asp.net 实现敏感词全局过滤

1、Global.asax 文件中写一下代码

 void Application_BeginRequest(object sender, EventArgs e)
    {
        //  在应用程序关闭时运行的代码
        if (Request != null && Request.Headers != null)
        {
            if (Request.Headers.AllKeys.Contains("Accept"))
            {
                if (!string.IsNullOrEmpty(Request.Headers["Accept"]))
                {
                    if (Request.Headers["Accept"].ToLower().Contains("text/html"))
                    {
                        Response.Filter=new ResponseFilter(Response.Filter);
                    }
                }
            }
        }
    }

2、新增过滤器类 ResponseFilter.cs 代码如下

using DotNet.Utilities;
using Lucene.Net.Util.Cache;
using System;
using System.Activities.Expressions;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Web;

/// <summary>
/// ResponseFilter 的摘要说明
/// </summary>


public class ResponseFilter : Stream
{
    #region properties 
    Stream responseStream;
    long position;
    StringBuilder html = new StringBuilder();
    #endregion
    #region constructor 
    public ResponseFilter(Stream inputStream)
    {
        responseStream = inputStream;
    }
    #endregion
    #region implemented abstract members 
    public override bool CanRead
    {
        get { return true; }
    }
    public override bool CanSeek
    {
        get { return true; }
    }
    public override bool CanWrite
    {
        get { return true; }
    }
    public override void Close()
    {
        responseStream.Close();
    }
    public override void Flush()
    {
        responseStream.Flush();
    }
    public override long Length
    {
        get { return 0; }
    }
    public override long Position
    {
        get { return position; }
        set { position = value; }
    }
    public override long Seek(long offset, System.IO.SeekOrigin direction)
    {
        return responseStream.Seek(offset, direction);
    }
    public override void SetLength(long length)
    {
        responseStream.SetLength(length);
    }
    public override int Read(byte[] buffer, int offset, int count)
    {
        return responseStream.Read(buffer, offset, count);
    }
    #endregion
    #region write method 
    public override void Write(byte[] buffer, int offset, int count)
    {
        string sBuffer = System.Text.UTF8Encoding.UTF8.GetString(buffer, offset, count);
        var pattern = new List<string>();//敏感词列表

        //
        //从配置文件 或任意其它地方 初始化 敏感词列表
        //
        foreach (string s1 in pattern)
        {
            if (!string.IsNullOrEmpty(s1))
            {
                if (s1.Contains("^"))
                {
                    var _ss = s1.Split(new[] { '^' }, StringSplitOptions.None);
                    sBuffer = sBuffer.Replace(_ss[0], _ss[1]);
                }
                else
                {
                    sBuffer = sBuffer.Replace(s1, "***");
                }
            }

        }
        byte[] data = System.Text.UTF8Encoding.UTF8.GetBytes(sBuffer);
        responseStream.Write(data, 0, data.Length);
    }
    #endregion
}